1. Field of the Invention
The present invention relates in general to humidifiers. In particular, the present invention relates to improved control systems to halt the operation of humidifiers upon certain sensed conditions or provide a signal upon such sensed conditions.
2. Description of the Related Art
Humidifiers for home use have been known for many years. Such humidifiers work upon one of several principles, such as a wicking humidifier or an ultrasonic humidifier. Regardless of the operating principal of the humidifier, such devices almost invariably include some type of control mechanism.
In the simplest form, such control mechanisms consist of an on/off switch to energize the motor and thus control operation of the humidifier. For several types of humidifiers, however, their particular arrangement and structural elements are such that additional control mechanisms may greatly aide in their operation or safety. For example, in wick and ultrasonic humidifiers it is often the case that the humidifier includes removable bottles of water which automatically dispense to increase the amount of time between provision of the humidifier with water, thus increasing its convenience to the user. In such an arrangement it has been known to provide sensors to detect the water level within the humidifier and/or the auxiliary water bottle, to notify the user as to a low water condition and/or to cease operation of the humidifier upon such a low water condition.
While sensors detecting the water directly (i.e. electric current passing through the water) could be placed within the bottle, such a sensor would have to be quite rugged, and therefore expensive, and additionally entails problems in communication from the sensor inside the bottle to the wiring of the humidifier outside the bottle. To avoid such problems, it has been known to sense not the actual presence (i.e. wetness) of the water, but rather the weight of the water. Arrangements which sense the water weight are shown in U.S. Pat. No. 2,956,417 to Lyman and DE 2 256 404 to Hei.beta.meier. These patents relate to dehumidifiers, and thus obviously employ a reverse arrangement where switching occurs upon accumulation, rather than dispersal, of water. However, both of these arrangements support the water container with a biasing spring in a manner such that the weight of the water within the container determines the position of the container. The final desired weight (in this case a full container) will place the container in a position to cause switching.
A conceptually similar arrangement, though reversed for use as a humidifier, is disclosed in U.S. Pat. No. 5,037,583 to Hand. In the Hand patent a water bottle is supported upon a spring which tends to bias the water bottle upward. Resting below a downward directed shoulder of the water bottle is an upwardly biased switch which controls operation of the humidifier motor. When the water bottle is not depleted the combined weight of the bottle and water will compress the supporting spring to position the bottle at its lowest position, such that the switch is maintained in the closed position and the humidifier motor will operate. When the water has sufficiently depleted such that the weight of the water bottle is greatly reduced, the biasing spring will lift the water bottle, positioning the bottle at its highest position, allowing the switch to open, ceasing operation of the humidifier motor or providing a signal.
While this arrangement of Hand is serviceable, there are various drawbacks. For example, the placement of the biasing spring directly below the water tank, in conjunction with the properties of the spring, will result in the water bottle being moved progressively upward as its weight is reduced. As such, the physical characteristics of the spring, physical dimensions of the water bottle and placement and sensitivity of the switch must be fairly accurate to ensure that the switch is opened only after full depletion of the water within the bottle.
Additionally, the typical dispensing arrangement for such water bottles is a valve which is only opened when the bottle is in the lowered position. As such, the progressive upward movement of the water bottle during depletion may result in the valve closing prior to depletion, and in the worst case, closing prior to operation of the switch. This would result in the motor continuing to run after the supply of water has been exhausted, or no signal to the user.
Finally, this dispensing arrangement operates upon a vacuum principal, such that large bubbles of air travel upward through the water in the bottle during the dispensing. Where the water bottle is in a position supported solely by the biasing spring, these forces may result in a vertical oscillation of the water bottle, which may accidently open the switch prior to the desired time.
The Hand arrangement also does not allow for the possibility of the operator desiring to continue operation of the fan after depletion of the water, such as to fully dry the wicking elements prior to storage.
Humidifiers are also typically provided with covering hoods which hide the water bottles and interior mechanisms of the humidifier for aesthetic reasons. Removing such covers to gain access to the water bottles may expose the operating mechanism for the humidifier. As such, the user or the operating mechanism of the humidifier may be subject to danger.